Field of the Invention
The invention relates to a host cell capable of producing at least four different enzymes chosen from the group of cellulases, hemicellulases and pectinases, a process for the preparation of said host cell, an enzyme composition produced by said host cell, a process for the production of an enzyme composition using said host cell, a process for the saccharification of lignacellulosic material using the enzyme composition and a process for the preparation of a fermentation product using the enzyme composition.
Description of Related Art
Carbohydrates constitute the most abundant organic compounds on earth. However, much of this carbohydrate is sequestered in complex polymers including starch (the principle storage carbohydrate in seeds and grain), and a collection of carbohydrates and lignins known as lignocellulose. The main carbohydrate components of lignocellulose are cellulose, hemicellulose, and pectins. These complex polymers are often referred to collectively as lignocellulose.
Bioconversion of renewable lignocellulosic biomass to a fermentable sugar that is subsequently fermented to produce alcohol (e.g., ethanol) as an alternative to liquid fuels has attracted an intensive attention of researchers since 1970s, when the oil crisis broke out because of decreasing the output of petroleum by OPEC. Ethanol has been widely used as a 10% blend to gasoline in the USA or as a neat fuel for vehicles in Brazil in the last two decades. More recently, the use of E85, an 85% ethanol blend has been implemented especially for clean city applications. The importance of fuel bioethanol will increase in parallel with increases in prices for oil and the gradual depletion of its sources. Additionally, fermentable sugars are being used to produce plastics, polymers and other biobased products and this industry is expected to grow substantially therefore increasing the demand for abundant low cost fermentable sugars which can be used as a feed stock in lieu of petroleum based feedstocks.
The sequestration of large amounts of carbohydrates in plant biomass provides a plentiful source of potential energy in the form of sugars, both five carbon and six carbon sugars that could be utilized for numerous industrial and agricultural processes. However, the enormous energy potential of these carbohydrates is currently under-utilized because the sugars are locked in complex polymers, and hence are not readily accessible for fermentation. Methods that generate sugars from plant biomass would provide plentiful, economically-competitive feedstocks for fermentation into chemicals, plastics, and fuels.
Regardless of the type of cellulosic feedstock, the cost and hydrolytic efficiency of enzymes are major factors that restrict the commercialization of the biomass bioconversion processes. The production costs of microbially produced enzymes are tightly connected with a productivity of the enzyme-producing strain.
With productivity of a strain is meant the amount of total protein or enzyme activity produced in the fermentation broth per time, for example kg protein/(m3 broth·year) or enzyme units/(m3 broth·year).
An enzyme unit is the ability of a defined amount of protein to convert a defined substrate under certain defined conditions.